Clinoidal meningiomas.

Meningiomas that arise at the anterior clinoid process are termed clinoidal meningiomas and are characterized by unique anatomopathologic correlates that result in unique clinical behavior. According to their site of origin, clinoidal meningiomas can be further divided into three subgroups, which also differ in their clinical presentation and surgical outcome. Clinoidal meningiomas are centered on the anterior clinoid process and grow upward with a small pedicle while causing hyperostosis of the anterior clinoid process itself. The optic nerve is frequently compressed and visual symptoms occur early and in most cases. Upon surgical resection, visual symptoms improve in a significant portion of patients. Cavernous sinus invasion is infrequent. With increasing size, however, clinoidal meningiomas tend to invade surrounding neurovascular structures including distal carotid branches, which results in poor surgical outcome. Most clinoidal meningioma cases are managed with surgery where the anterior clinoid process is also removed along with the tumor either with an extradural or an intradural approach. Standard as well as minimal invasive and skull base approaches are advocated by different groups, but the results are comparable. Surgical results are very good in most cases with low mortality and morbidity. Invasion of the internal carotid artery, optic nerve, or distal carotid branches increase the risk of a postoperative residual. Recurrences are observed and usually managed with Gamma-Knife radiosurgery.